Efficiency Of Mg Research Articles

Effects of Al and Sn on microstructure, corrosion behavior and electrochemical performance of Mg–Al-based anodes for magnesium-air batteries

Three types of Mg–Al-based anodes Mg–3Al–Zn, Mg–6Al–Zn, and Mg–6Al–Sn (wt.%) alloys were produced. The influences of Al and Sn on microstructure, corrosion behavior, electrochemical property, and battery performance were studied. The experimental results show that the introduction of Al and Sn leads to the significant grain refinement and the decrease of hydrogen evolution rate of Mg–Al-based anodes. The more Al element added in alloy, the more β-Mg17Al12 phases scattered at the grain boundaries, which can accelerate the dissolution of magnesium matrix. Thus, Mg–6Al–Zn manifests stronger discharge activity than Mg–3Al–Zn. The added Sn is capable to propagate Mg2Sn phases along the grain boundaries and to suppress the precipitate of coarse β-Mg17Al12 phases in Mg–6Al–Sn. Significantly, the fine grain with tiny second phases existed in Mg–6Al–Sn is beneficial to facilitate the self-peeling of discharge products by forming the micro-cracks on the alloy surface during discharge process. The results suggest that Mg–6Al–Sn exhibits a higher electrochemical activity and utilization efficiency, specifically, a better discharge stability at the large current density for long-time. The average cell voltage, power density, specific capacity and anodic efficiency of Mg–6Al–Sn anode for Mg-air battery within 12 h at 50 mA cm−2 were 1.097 V, 54.85 mW cm−2, 1423 mA h g−1 and 63.7%, respectively.

Removal phospate-containing detergent wastewater by Mg–Al(NO3) layered double hydroxide

Detergent wastewater contains high phosphate concentrations, so that if the wastewater is directly disposed of into a ditch or river then the wastewater can cause water pollution and eutrophication. Layered double hydroxides (LDHs) are synthetic materials with positively charged pyruvate type coatings of mixed metal hydroxides by chemical precipitation method. The purpose of this study is to find out the efficiency of Mg–Al(NO3) LDH on phosphate-containing detergent wastewater adsorption. The morphological structure of LDH by the SEM-EDS analysis method shows a loose lamellar structure with a particle size of about 1 μm, and the composition of Mg–Al(NO3) LDH by the XRF analysis method shows that the Mg and Al elements dominate more than other elements. Batch adsorption experimental conducted for detergent wastewater, which is where in this study the phosphate content was of ca. 51.50 mg / L. The equilibrium time of the adsorption process using Mg–Al(NO3) LDH is achieved after 60 minutes. The mole ratio of Mg : Al composition of LDH in the adsorption process has slightly affects the decrease in phosphate shown by a mole ratio of 1 : 1, 2 : 1 and 3 : 1 using Mg–Al (NO3) LDH as adsorbent at dose of 1 g, stirring rate of 100 rpm, 60 minutes, and at room temperature that is equal to 4.15 mg/L, 4.14 mg/L and 4.08 mg/L, respectively. Mg–Al(NO3) LDH is a promising adsorbent for phosphate removal in detergent wastewater.

Efficiency of Magnesium Hydroxide Capping and Amendment to Control Phosphorus Release from Sediments

Eutrophication of freshwater bodies has become a global environmental problem, and phosphorus (P) has been identified as one of the key limiting factors responsible for this eutrophication problem. Reducing internal P release is crucial to the control of the eutrophication of freshwater bodies besides reducing the input of external P. To control sedimentary P release, magnesium hydroxide[Mg(OH)2] was applied as a capping and amendment material in this study. The adsorption performance of phosphate on Mg(OH)2 was investigated in batch mode, and the effect of Mg(OH)2 capping and amendment on the mobilization of P in sediments was studied using sediment incubation experiments. Results showed that Mg(OH)2 exhibited good adsorption performance toward phosphate. The phosphate removal efficiency of Mg(OH)2 increased with increasing adsorbent dosage. The adsorption equilibrium data of phosphate on Mg(OH)2 could be better described by the Freundlich and Dubinin-Radushkevich isotherm models compared to the Langmuir isotherm model. Mg(OH)2 capping and addition both could effectively control the release of reactive soluble P (SRP) from sediments into the overlying water, resulting in a low concentration of SRP in the overlying water under Mg(OH)2 capping and amendment conditions. Mg(OH)2 capping and amendment both could reduce pore water SRP in the uppermost sediment (0-10 mm), which played a key role in the control of the release of SRP from sediments into the overlying water. The as-prepared Mg(OH)2 possessed a much higher phosphate adsorption ability than commercial Mg(OH)2, and the former also had a higher controlling efficiency of sedimentary P release than the latter. In summary, Mg(OH)2 is a promising capping and amendment material for the control of internal phosphorus release in freshwater bodies.

Excellent Ultraviolet Photocatalytic Efficiency of Mg 2+ Doped ZnO and Analysis on Its Synergetic Effect

Excellent Ultraviolet Photocatalytic Efficiency of Mg 2+ Doped ZnO and Analysis on Its Synergetic Effect

Boosting the doping efficiency of Mg in p-GaN grown on the free-standing GaN substrates

The Mg doping efficiency is found to be drastically enhanced in the p-GaN films grown on the free-standing GaN substrates by metal organic chemical vapor deposition. The free hole concentrations are five and ten times higher in the lightly and heavily Mg-doped homoepitaxial p-GaN, respectively, than those in the p-GaN-on-GaN/sapphires grown and activated at the same conditions although the Mg incorporation concentrations {[Mg]} are much lower. The indication of the p-type conductivity in the photoluminescence spectra at room temperature in p-GaN-on-GaN substrates is found to be the dominant ultraviolet luminescence band located at around 3.26 eV. This behavior is different in the heteroepitaxial p-GaN, for which the fingerprint of the p-type conductivity is the emergence of blue luminescence bands at around 2.9 eV. The markedly enhanced activation efficiency is attributed to the suppression of self-compensation centers in the high-quality homoepitaxial films. The Mg-Ga-O disordered layer, which is typically observed on the surface of p-GaN-on-GaN/sapphires due to the Mg diffusion along edge-type dislocations, is also inhibited on the homoepitaxial p-GaN film, which is beneficial for the stable operation of the vertical-type metal-oxide-semiconductor field effect transistors.

Clarifying the decisive factors for utilization efficiency of Mg anodes for primary aqueous batteries

Low anodic efficiency of metallic Mg, which results in low discharge capacity and specific energy density, hinders the wider application of aqueous primary Mg batteries. In this work, we clarify the decisive factors effecting the utilization efficiency of Mg anodes. Anodic efficiency of several Mg anodes at different current densities is measured in 3.5 wt% NaCl electrolyte. The contribution of self-corrosion at open circuit potential and at constant applied current to efficiency of Mg anodes is compared. Additionally, efficiency loss caused by detachment of undissolved metallic portions, namely “chunk effect”, is determined with a proposed new approach. The effect of self-corrosion and “chunk effect” on anodic efficiency is assessed accordingly. The results indicate that “chunk effect” can also result in large efficiency loss of Mg anodes, especially at low current densities, which, in some cases, could exceed the loss caused by other mechanisms of self-corrosion of anode substrate. Hence, attention should be paid to both aspects when developing novel Mg anodes with high anodic efficiency, particularly for application in long-term low-power battery system.

Expanded graphite assistant construction of gradient-structured char layer in PBS/Mg(OH)2 composites for improving flame retardancy, thermal stability and mechanical properties

It is a great challenge to improve the flame retardancy of polymer materials by adding eco-friendly magnesium hydroxide (Mg(OH)2) but simultaneously maintain satisfied mechanical performances. In this study, expanded graphite (EG) as a synergist was introduced into poly(butylene succinate) (PBS)/Mg(OH)2 system to investigate the effect of EG on their flame retardancy, thermal stability and mechanical properties. The results showed that only addition of 5 wt% EG into PBS/20 wt%Mg(OH)2 resulted in excellent flame retardancy, including that the LOI was 29.4%, the UL-94 rating reached to V0, and the PHRR decreased by 73%. These flame retarded parameters were comparable or even better than that of PBS/40 wt%Mg(OH)2 composites. More importantly, PBS/20 Mg(OH)2/5 EG presented much better thermal stability and mechanical properties than PBS/40 wt%Mg(OH)2, indicating a balanced improvement on comprehensive performances of PBS. Based on the comparison with PBS/20 Mg(OH)2/5Graphene(Gr) system and the structure analysis for residual chars, the mechanism for improved flame retardancy was attributed to the formation of gradient-structured char layer due to the helpful thermal expansion process of EG together with the decomposition of Mg(OH)2 during combustion, resulting in better barrier action to heat, oxygen and flammable gases via “labyrinth effect”. As far as we know, it is the first report that gradient-structured char layer was discussed in flame retarded polymer systems. Hence, this work provides not only a high-efficient synergist to improve the flame retardant efficiency of Mg(OH)2, but also useful guidelines to design polymer composites with balanced comprehensive performances.

Sulfur trioxide removal performance of alkaline sorbents injection in the temperature range 400–705 °C: a pilot‐scale study

AbstractBACKGROUNDSulfur trioxide (SO3) in coal combustion flue gas can adversely affect power plant equipment and the environment. In this work, the removal of SO3 with typical sodium (Na), magnesium (Mg) and calcium (Ca)‐based sorbents was investigated at a pilot‐scale facility in the temperature range 400–705 °C.RESULTSThe injection of sodium bicarbonate (NaHCO3) showed the highest SO3 removal efficiency, which was ∼85% at the sorbent/SO3 molar ratio of 2 with the gas residence time of 1 s. This is much higher than that of calcium hydroxide (Ca(OH)2) (∼25%) and magnesium hydroxide (Mg(OH)2) (∼30%). The removal efficiency of Mg(OH)2 and Ca(OH)2 increased with increasing the reaction temperature from 400 to 705 °C. With the addition of 800 ppm sulfur dioxide (SO2), the adsorption of SO3 on alkaline sorbents was inhibited due to the competitive adsorption, which caused SO3 removal efficiency to decrease by 5–12.5%. When injecting the sorbents in slurry form, the removal efficiency was found to be two times higher than that in powder form.CONCLUSIONNaHCO3 is the most effective sorbent comparing to Mg(OH)2 and Ca(OH)2. To increase the SO3 removal efficiency, the alkaline sorbents should be injected in the high temperature zone in flue gas. It is recommended to inject the sorbents in slurry form instead of injecting powders directly to achieve high removal efficiency. © 2019 Society of Chemical Industry

Green synthesis of silver doped nano metal oxides of zinc & copper for antibacterial properties, adsorption, catalytic hydrogenation & photodegradation of aromatics

Silver doped copper and zinc nano metal oxides were synthesized in the presence of Sida rhombifolia leaf extract by self propagating sol-gel autocombustion process. X-ray diffraction studies indicated the formation of wurtzite hexagonal phase for ZnO, monoclinic for CuO and FCC structure for silver nanocomposites. The surface morphology of nanoparticles were studied using FESEM. FTIR studies confirmed the presence of silver & M–O bonds. UV–vis DRS studies revealed that silver doping reduced the band-gap energy which overcomes fast recombination rate of electron-hole pairs of the nanoparticles. TGA studies indicated enhanced thermal stability of doped nanocomposites. Hydrogenation of 4-nitrophenol to 4-aminophenol with NaBH4 showed that Ag/ZnO & Ag/CuO exhibited greater photoreduction capacity than undoped ZnO & CuO. ZnO, Ag/ZnO, CuO & Ag/CuO nanocomposites have antagonistic effect on the growth of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeroginosa, Streptococcus mutans and Staphylococcus aureus with greater inhibition zones. Ag/CuO NPs exhibited the highest sensitivity against various bacterial strains with MIC below 1 mg. Ag/CuO nanorods showed excellent adsorption properties with high removal capacity of MG of about 90%. Kinetic, thermodynamic and equilibrium studies on adsorption of MG onto Ag/CuO nanorods was carried out. The photocatalytic activity of ZnO and Ag/ZnO nanocomposites was investigated by studying the degradation of methylene blue & malachite green under UV irradiation. Ag/ZnO exhibited better photodegradation efficiency of MG & MB and follows pseudo first order kinetic model. Thus the simple, low-cost and eco-friendly herbal synthesis of oxides of silver doped zinc & copper provides nanocomposites with multifunctional applications.

Electrolyte Additive Enabling Conditioning-Free Electrolytes for Magnesium Batteries.

Most electrolytes for rechargeable Mg batteries require time-consuming conditioning or precycling process to achieve a fully reversible Mg deposition/dissolution, which hinders the normal operation of Mg batteries. This study details a simple and effective method for eliminating this conditioning behavior using heptamethyldisilazane (HpMS) as an electrolyte additive. It was found that the HpMS additive greatly increases the current density and Coulombic efficiency of Mg deposition/dissolution from the initial cycles in various sulfone and glyme solutions containing MgCl2 or Mg(TFSI)2. The beneficial effect of HpMS was ascribed to its ability to scavenge trace water in the electrolytes and remove Mg(OH)2 and Mg(TFSI)2-decomposition products from the Mg surface. Considering its applicability for a wide range of Mg electrolytes, the use of HpMS is expected to accelerate the development of practical Mg batteries.

Substantial effect of magnesium incorporation on hydroxyapatite/carbon nanotubes coatings on metallic implant surfaces for better anticorrosive protection and antibacterial ability

This work elucidates the antibacterial and corrosion protection efficiency of Mg substituted hydroxyapatite/multiwalled carbon nanotube composite coated 316L SS implant. A novel spray deposition method was adopted for the composite coating. The fabricated HA/MWCNT and Mg-HA/MWCNT films were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Field emission scanning electron microscopy. Mg addition played a significant role to decrease the crystallinity and increase the surface area of the HA/MWCNT composite. The vibrational spectra show shift in the PO stretching vibration of PO43− group at 1127 cm-1 after Mg substitution. The morphology of Mg-HA/MWCNT coating revealed spherical shaped apatite crystals with interconnected network like microstructure which is beneficial for bone tissue engineering. The Mg-HA/MWCNT nanocomposite revealed a better antibacterial activity against E.coli with a high zone of inhibition of 16 mm. The electrochemical behaviour of the Mg-HA/MWCNT/SS in simulated body fluid demonstrated an increased polarization resistance with decreased current density (icorr). Compared to bare HA/CNT coated implant, the Mg ions substituted implant revealed superior corrosion resistance with a lower corrosion penetration rate. Thus, the bioactive Mg-HA/MWCNT composite coated 316L SS implant developed with superior antibacterial and anticorrosion properties is considered as the potential aspirant for orthopaedic applications.

N- and P- type Doping in Al-rich AlGaN and AlN

Significant challenges in point defect control in AlGaN epitaxy has precluded commercialization of AlGaN based devices. Si is typically employed as n-type dopant in AlGaN and exhibits a low activation energy (<50 meV) in AlxGa1-xN with x<0.8. However, Si doped AlGaN exhibits a “knee behavior” resulting in a conductivity and carrier concentration maxima at a specific Si concentration. Hence a high doping limit exists for Si in AlGaN that lowers the maximum achievable carrier concentrations that are necessary for AlGaN based power electronics. Similarly, a low doping limit (a minimum achievable carrier concentration with a corresponding maximum mobility) exists in AlGaN similar to that in GaN which precludes implementation of AlGaN power electronics that require low doped drift regions. Along the same lines, p-type doping is achieved with Mg, but high activation energies preclude its technological implementation. Following results in GaN, compensating point defects are also expected to play a major role in determining the doping efficiency of Mg, even if methods to “reduce” its activation energy are found. Hence a major “point defect problem” exists in AlGaN that needs to be solved for implementation of AlGaN technology. In this work, we update on three different achievements: (1) identifying and controlling point defects for efficient n-type doping in AlGaN, (2) implantation as a method for achieving high n-type conductivity in AlN and (3) the possibility of high conductivity p-type AlGaN. All these achievements are built upon a point defect control (PDC) framework based on a systematic chemical potential control (CPC) and defect quasi Fermi level control (DQFL). In CPC, the growth environment variables are related to the defect formation energy by determining and controlling the Al,Ga,N and impurity chemical potentials. This helps optimize the growth environment accordingly for minimal point defect incorporation or generation. In DQFL control, the defect quasi Fermi level, the Fermi level describing the probability of the defect level being occupied/unoccupied, is modified by introducing excess minority carriers (by above bandgap illumination). This leads to an increase in the compensating point defect formation energy, reducing their concentration. Both control schemes provide for a theoretical framework that provides a quantitative relationship between point defect formation energies and growth process parameters. CPC based targeted reduction requires knowledge of the defects responsible and accordingly, we identify the point defects responsible for knee behavior in n-type AlGaN as most likely vacancy-silicon complexes and low doping limit as CN. Note that threading dislocations and vacancy-oxygen complexes are also expected to be compensating and contribute to the low doping limit. Utilizing the vacancy-silicon complex and CN in Al0.7Ga0.3N as a case study, we demonstrate control over the knee behavior (improving the peak carrier concentration by impeding the formation VIII-SiIII complexes) and low doping limit (achieving lower carrier concentrations by reducing the compensating impurity (CN) density) in Al0.7Ga0.3N by controlling the chemical potentials of III/N and growth temperature with excellent agreement with quantitative theoretical predictions. These concepts are further used in Si implanted AlN where a reduction in the formation of vacancy-silicon complexes during implantation annealing is necessary. This was achieved by implementing DQFL control during the implantation annealing stage. Such process led to an increase of nearly 3 orders of magnitude in the conductivity of n-type AlN at room temperature. Finally, after recognizing the importance of point defect reduction during doping, significant achievements in p-type AlGaN were realized. Lower Mg activation energies than those previously reported were observed leading to significant p-type conductivity in AlGaN. All these results support our PDC framework and the utility of formation energies from equilibrium formalism typically employed in DFT in predicting defect incorporation in non-equilibrium and high temperature MOCVD growth.

Carbon Cloth Supported Nano-Mg(OH)2 for the Enrichment and Recovery of Rare Earth Element Eu(III) From Aqueous Solution.

Nano-Mg(OH)2 is attracting great attention as adsorbent for pre-concentration and recovery of rare earth elements (REEs) from low-concentration solution, due to its superior removal efficiency for REEs and environmental friendliness. However, the nanoparticles also cause some severe problems during application, including aggregation, blockage in fixed-bed column, as well as the difficulties in separation and reuse. Herein, in order to avoid the mentioned problems, a carbon cloth (CC) supported nano-Mg(OH)2 (nano-Mg(OH)2@CC) was synthesized by electrodeposition. The X-ray diffraction and scanning electron microscopy analysis demonstrated that the interlaced nano-sheet of Mg(OH)2 grew firmly and uniformly on the surface of carbon cloth fibers. Batch adsorption experiments of Eu(III) indicated that the nano-Mg(OH)2@CC composite maintained the excellent adsorption performance of nano-Mg(OH)2 toward Eu(III). After adsorption, the Eu containing composite was calcined under nitrogen atmosphere. The content of Eu2O3 in the calcined material was as high as 99.66%. Fixed-bed column experiments indicated that no blockage for Mg(OH)2@CC composite was observed during the treatment, while the complete blockage of occurred to nano-Mg(OH)2 at an effluent volume of 240 mL. Moreover, the removal efficiency of Mg(OH)2@CC was still higher than 90% until 4,200 mL of effluent volume. This work provides a promising method for feasible application of nanoadsorbents in fixed-bed process to recycle low-concentration REEs from wastewater.

Assessment of selected macroalgae for use in a biological hybrid system for treating sulphur in acid mine drainage (AMD)

Filamentous algae biomass is very limited in aerobic constructed wetlands and totally absent in anaerobic constructed wetlands. Its contribution to the removal of sulphur from acid mine drainage will therefore rarely reach a significant level if not used in association with secondary algae treatment ponds as part of a biological hybrid treatment system. Although a high sulphur concentration has a lower environmental impact than dissolved metals and acidity, it does have an adverse impact on water quality. The current study employed selected macroalgal species under laboratory conditions to determine the bioaccumulation of sulphur (S) and other important algal growth elements such as calcium (Ca), magnesium (Mg) and phosphorus (P) from acid mine drainage (AMD) water and treated constructed wetland water at different pH values. Following exposure of the macroalgae to AMD and treated constructed wetland water for 192 h, Microspora tumidula showed the highest bioaccumulation of S and P which occurred at a pH of 5. Oedogonium crassum showed the highest bioaccumulation of Ca and Mg at a pH of 7. The results also showed that the accumulation efficiency of Mg by all three macroalgal species increased significantly as the pH increased. The filamentous species Oedogonium crassum and Klebsormidium klebsii showed very little increase in chl-a (mg g−1 fw) and ash free dry weight (mg g−1 AFDW) after exposure to the mine and treated constructed wetland water after 192 h at all four pH ranges in comparison to the species M. tumidula. However, the species M. tumidula show significant increases in both chl-a (mg g−1 fw) and mg g−1 AFDW at pH values 5, 6.14 and 7. The study established that the species M. tumidula is a good candidate for use in a biological hybrid system for treating sulphur-rich acid mine drainage.

NutsFor a process-oriented model to simulate nutrient and isotope tracer cycling in forest ecosystems

We developed a process-oriented model called NutsFor that simulates nutrient cycling of major cations (Ca, Mg, K, Al, NH4, Na) and anions (NO3, SO4, Cl) and the stable isotope tracers for each of the respective elements at the scale of an ecosystem (isotopic fractionation are not simulated). We tested the ability of NutsFor to reproduce major element and stable isotope tracer (26Mg and 44Ca) cycling with the data from 35-yr old beech stand in France. NutsFor correctly reproduced the measured trends in soil solution chemistry for most major elements. The high similarity between modeled and measured distribution of 26Mg and 44Ca tracers in the ecosystem provided a unique and robust way to evaluate the hypotheses grounding the model and study the efficiency of Mg and Ca cycling at this very nutrient-poor site.

Microstructures and electrochemical corrosion properties of Mg–Al–Pb and Mg–Al–Pb–Ce anode materials

Mg–Al–Pb alloy is a good candidate for the anode material of magnesium seawater battery. For improving the low current utilization efficiency of Mg–Al–Pb alloy, the influence of Ce on the microstructures and electrochemical corrosion properties in a 3.5% NaCl solution was investigated using scanning electron microscope and electrochemical measurements. The results indicate that Ce refines the grain structure of Mg–Al–Pb alloy. The formation of strip Al11Ce3 second phase promotes the uniform distribution of Mg17Al12 phase in Mg–Al–Pb–Ce alloy. The addition of cerium accelerates the discharge activity of Mg–Al–Pb alloy. Due to a large number of cathodic Al11Ce3 and Mg17Al12 phases, Ce promotes the micro-galvanic corrosion and leads to larger corrosion current density and hydrogen evolution rate in Mg–Al–Pb–Ce alloy than those in Mg–Al–Pb alloy. However, Mg–Al–Pb alloy expresses smaller utilization efficiency than Mg–Al–Pb–Ce alloy because of grain detachment.

Ignition and combustion of boron-based Al·B·I2 and Mg·B·I2 composites

Stable ternary powders of Al·B·I2 and Mg·B·I2 composites of interest for agent defeat applications were prepared by mechanical milling. All powders contained 20wt.% of iodine. Powder ignition was characterized using a heated filament experiment. Ignition kinetics was compared to the kinetics of events occurring upon slow heating of these materials in thermo-analytical experiments. Individual particle combustion was studied by seeding the powder into a premixed hydrocarbon–air flame. Both particle burn times and temperatures were measured optically. Aerosol combustion of the powders was tested in a constant volume explosion chamber. Ignition temperatures for the Mg·B·I2 composites were lower than those for the Al·B·I2 composites. Iodine release occurring due to the formation of AlB2 and MgB2 was a likely ignition trigger for Al·B·I2 and Mg·B·I2 composites, respectively. The burn times of these composites were longer than those for pure Al and Mg powders. Burn times for Mg·B·I2 particles were shorter than for the same size particles of Al·B·I2. Combustion temperatures of the composite powders were lower than those of pure Al and Mg. In aerosol combustion, the rate of pressurization and maximum pressure were inversely proportional to the concentration of boron. The combustion efficiency was expressed through a ratio of the experimental maximum pressure to that predicted by a thermodynamic equilibrium calculation. This efficiency was the same for Al and Al·B·I2 composites. The efficiency for Mg·B·I2 composites exceeded that of pure Mg.

A conditioning-free magnesium chloride complex electrolyte for rechargeable magnesium batteries

Catalytic dissolution of Mg metal in THF leads to a highly stable electrolyte for rechargeable magnesium batteries which share many common features with MACC, but does not require an onerous conditioning process. The high Mg to Al ratio in the electrolyte promotes 100% coulombic efficiency for Mg in the first cycle.

Recovery of magnesium and potassium from biotite by sulfuric acid leaching and alkali precipitation with ammonia

A process for the recovery of magnesium (Mg) and potassium (K) from biotite was developed using sulfuric acid leaching and precipitation with ammonia. The optimum conditions for dissolution of biotite were found to be sulfuric acid solution of 2.5mol/L, sulfuric acid/biotite ratio of 4mL/g, leaching temperature of 90°C and leaching time of 2h. Under these conditions, the leaching efficiency of Mg and K was found to be 95.8% and 94.9% respectively. By using the solubility differences of corresponding elements, a two-step precipitation process was applied to remove Fe and Al and recovery of Mg. Subsequently, magnesium hydroxide was prepared by precipitation from the leach solution with ammonia as the precipitant. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses showed that the high purity Mg(OH)2 existed in the form of flower-like spherical aggregation. Furthermore, the final solution of ammonium–potassium sulfate can be used for agricultural compound fertilizer.

The Unexpected Discovery of New Mg Complexes As Electrolytes for Rechargeable Magnesium Batteries

The electrolytes play a pivotal role in the multivalent batteries. Here we will report the unexpected discovery of new complexes as electrolytes for magnesium batteries. Eliminating the usage of Lewis acids, the electrolytes are safer than conventional magnesium organohaloaluminate. The electrolytes have a high coulombic efficiency for Mg plating/dissolution and the anodic stability is increased to 3.3 V vs Mg. The preparation and characterization of the new electrolytes will be presented, including the syntheses, multinuclear NMR spectroscopy, the hypothesis of the product formation, the electrochemical characterization such as ionic conductivities and transport numbers. The capabilities of the electrolyte with Chevrel Phase Mo6S8 and other cathodes will also be discussed. Figure 1